Conduction-Band and Surface-State Critical Points in Si: An Inverse-Photoemission Study

Abstract

From measurements of the dispersion of the lowest two conduction bands in silicon by $k$-resolved inverse photoemission the energies of the ${L}_{1}^{c}$ and ${L}_{3}^{c}$ critical points were determined as 2.40\ifmmode\pm\else\textpm\fi{}0.15 and 4.15\ifmmode\pm\else\textpm\fi{}0.10 eV relative to the valence-band edge, respectively. A comparison with energies derived from photoemission and optical data reveals a large excitonic lowering of the ${E}_{1}$ transition by 0.5\ifmmode\pm\else\textpm\fi{}0.2 eV. The lowest unoccupied surface state on the Si(111) 2\ifmmode\times\else\texttimes\fi{}1 surface at $\overline{\ensuremath{\Gamma}}$ is identified at 1.2\ifmmode\pm\else\textpm\fi{}0.1 eV.